This invention relates to an ultrasonic imaging apparatus and a method of forming an ultrasonic image of an object, the apparatus and method being based on the aperture synthesis technique and suitable for a high resolution imaging.
The conventional aperture synthesis technique is intended to achieve an enlarged receiving aperture frame, in which a similar ultrasonic beam is transmitted several times and the received signals are combined by switching receiving partial apertures so as to obtain a total-aperture reception signal, as disclosed in JP-A No. 58-132677 (corresponding to U.S. patent application Ser. No. 769,805 filed on Aug. 27, 1985 which is a continuation application of U.S. patent application Ser. No. 463,652 filed on Feb. 3, 1983 now abandoned). The above technique, however, does not deal at all with switching noise caused due to the fact that different transducers are selected for ultrasonic beam transmission and reception.